THE LIFE IN THE SEA. 19 
either no tides at all or only such as to be hardly perceptible, there 
exist a number of vegetables and animals which belong to the open 
sea, which the waves or currents seldom or never cast upon the 
beach. There are others so fugitive or so firmly attached to the 
rocks, that they never can be examined except in the places where 
they live. It is therefore necessary to catch them floating on the 
surface of the water or to follow them into their native depths. 
This is why naturalists who are seriously intent upon studying the 
life of the sea must carry on their researches on the bosom of the 
DREDGERS. 
water, and not on the shores. Many of these explorers use for 
this purpose dredges, sounding lines, and other proper instruments 
for scraping and breaking the hard rocks. In his voyage round 
the coasts of Sicily, Milne Edwards hit upon the excellent idea of 
using the apparatus invented by Colonel Paulin, the veteran chief of 
the Paris fire brigade. This apparatus consists of a metal helmet 
provided with a glass visor, which is fixed to a padded collar 
by means of a leathern fringe. This helmet is really a diving- 
bell in miniature. It communicates with a forcing-pump by 
means of a flexible tube. Four men are employed to work the 
pump, two at a time; other two hold the end of a rope, which 
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